This research is designed to determine neuroanatomical and neurochemical correlates of addictive and aggressive/impulsive behavior in human subjects. The principal focus of these studies is the measurement and correlation of regional cerebral glucose metabolic activity, using positron emission tomography (PET), brain volumes using magnetic resonance imaging (MRI), cerebrospinal fluid metabolites, and measures of impulsive/aggressive behavior and excessive alcohol consumption. During the past year we have completed a PET study comparing serious head injury and secondary sociopathy. Examining the brains of head injured persons with secondary sociopathy provides insight to structural and functional pathology associated with antisocial behavior and may also provide insight to sociopathy not acquired as a result of head trauma. When we compared the energy use in the brains of ten men who became irresponsible, socially inappropriate, and impulsively aggressive following a serious head injury with twelve healthy men we found significantly lower energy use in five brain regions only; the lateral orbital cortex on both sides of the brain, a region of the right prefrontal cortex known as Brodman area 32, the right medial thalamus, and the right caudate nucleus. Energy use of the entire brain was not lower among the head injured men. The largest differences in brain energy use between normal and head injured men were in the right medial prefrontal cortex, the right thalamus, and right caudate. Energy use in these three brain regions was closely associated with the severity and amount of aggressive behavior in which subjects had engaged since their injury. Comparison of the size of brain structures using MRI yielded results similar to our PET results. The volume of the entire brain did not differ between the two groups, but the volume of the right medial prefrontal cortex (Brodman area 32), the right thalamus, and right caudate was significantly smaller among the head injured men compared to the healthy men. The size of these three regions on the left side of the brain did not differ between the head injured and healthy men. We have also continued studies of brain structure in alcoholics and controls. Controlling overall brain volume we have found significant reductions in the volumes of the hippocampus in alcoholics. Studies of other brain regions such as thalamus, caudate, and mesial frontal cortex are planned.